The invention generally relates to covers over the openings of large containers, such as transfer trailers. More specifically, the invention relates to a control mechanism for opening and closing such covers.
Many different types of large containers are used for hauling loads and waste, such as solid waste, construction debris, landscape materials, recyclables, etc. One such type are wheeled containers designed for hauling by trucks, known as xe2x80x9ctransfer trailersxe2x80x9d. Transfer trailers are typically rectangular-shaped with open tops. Covers over the open tops are typically provided to prevent the load from spilling, sliding or being blown out the top of the container during transport. These covers have taken various forms in the past, including tarpaulin, lightweight nylon doors, open mesh plastic screens, etc. Some past trailer cover doors have consisted of two half-doors each rotating about a pivot point located adjacent each sidewall of the trailer. However, the doors may be 45 feet in length, and may each weigh 400 pounds, for example. Thus, the doors may be too heavy to manually open and close, and for this purpose hydraulic power mechanisms have been employed.
Known rotation control mechanisms for flip tops have disadvantages. They do not maintain control of the cover door(s) during their entire rotation. Thus, once a door has been rotated over-center, conventional powering mechanisms allow it to free fall down and possibly be damaged upon impact with the outer sidewall of the container. In the case of hazardous waste, for example, the doors need to be tightly sealed, such as by using a rubber gasket seal, and this may be impossible if the doors are sufficiently damaged, such as being bent. Further, such powering mechanisms have been relatively expensive since they have required relatively large hydraulic pressures to accomplish door rotation.
Accordingly, it is an object of the present invention to provide a control mechanism for a trailer cover which maintains control of the cover doors during their entire rotation, preventing damage to the doors and/or the trailer.
It is another object of the invention to provide a control mechanism for covering a container opening which requires relatively low hydraulic or air pressure as compared to conventional control mechanism, enabling the more economic manufacture and use of the trailer.
The following terms are used in the claims of the patent as filed and are intended to have their broadest meaning consistent with the requirements of law. Where alternative meanings are possible, the broadest meaning is intended. All words used in the claims are intended to be used in the normal, customary usage of grammar and the English language.
Container: Any large receptable, including but not limited to a transfer trailer, such as containers used for holding and/or hauling loads or waste.
Linkage mechanism: A system of links or bars which are joined together.
The objects mentioned above, as well as other objects, are solved by the present invention, and overcome disadvantages of prior art mechanisms for controlling the opening and closing of large container covers, such as transfer trailer doors, while providing new advantages not believed associated with such mechanisms.
In one preferred embodiment, a device is provided for controlling the opening and closing of at least one door covering at least part of an opening of a container, such as a transfer trailer or other container. The door(s) may be pivotally or otherwise attached to various locations on the container such as at an upper edge of the container, for example. The device includes one or more power mechanisms attached to the container for driving rotation of the door. The power mechanism may include a hydraulic cylinder or an air-powered cylinder, for example. At least one linkage mechanism is connected to the power mechanism, and transfers force from the power mechanism to open or close the door, such as by driving its rotation. Preferably, the door(s) remains under constant control, such as under constant rotational control, of the power mechanism during its opening and closing. Preferably, the door rotates through at least about 180xc2x0 and, more preferably, rotates through at least about 270xc2x0.
In a preferred embodiment, at least one arm is provided which is slidably and pivotally connected to the at least one door and also pivotally connected to the container, and the linkage mechanism substantially increases the rotational mechanical advantage imparted by the power mechanism to the at least one arm. In a preferred embodiment, the linkage mechanism may include first and second links. The first link may be pivotally connected to the power mechanism and to a wall of the container, and the second link may be pivotally connected to the first link and to the arm. In one embodiment, one link may be curved and the other may be straight, allowing the use of links in the same or substantially the same plane. The curved link may be pivotally attached to the container, and the straight link may be pivotally attached to an intermediate portion of the arm and also pivotally attached to the curved link. In an alternative embodiment, two straight links may be used, in which case they may be designed to be in different or substantially different planes. In a particularly preferred embodiment, a first four-bar linkage connected to the power mechanism drives a second four-bar linkage connected to the door.
In a particularly preferred embodiment, the ratio of cylinder pressure (psi) to door weight (pounds), or the xe2x80x9ccylinder pressure-to-door weight ratioxe2x80x9d is preferably less than about 3.0, and more preferably less than about 2.0. Also with the present invention the ratio of cylinder force to door weight, or the xe2x80x9ccylinder force-to-door weight ratioxe2x80x9d is about 22, and in preferably in the range of about less than 30, and more preferably less than about 25. In a preferred embodiment, a power mechanism employs at least one hydraulic cylinder under pressure of less than about 2000 psi, and more preferably less than about 1000 psi.